Vastly prefer Prague over London, London is too expensive for what you get, rather pay a ticket to New York than spent my money in London.
If you choose Spain, great, but do it on the mainland close or in Barcelona or Madrid, pain to find connections to smaller airports.
26-30th June is a bad date, that period is probably one of the fullest in Europe: weddings, festivals, baptisings ... everyone plans their stuff during that period
btw would be great if some of the Amsterdam shows would move to other cities from time to time, Amsterdam isn't that appealing if you're not into weed
